[42183] in Cypherpunks
Re: MD5 weakness ? [was Re: Netscape Logic Bomb detailed by IETF]
daemon@ATHENA.MIT.EDU (Steve Bryan)
Tue Oct 24 16:47:10 1995
Date: Tue, 24 Oct 1995 15:08:51 -0500
To: fc@all.net (Dr. Frederick B. Cohen)
From: Steve Bryan <sbryan@maroon.tc.umn.edu> (Steve Bryan)
Cc: cypherpunks@toad.com
Dr. Frederick B. Cohen writes:
>In the case of the trust being placed in MD5 by Netscape, the assumption
>being made (without adequate support as far as I can tell) is that an
>MD5 checksum cannot be forced, through a chosen plaintext attack, to
>yield checksums of 1, 2, 3, 5, 7, 9, ... on up to enough primes to
>allow the known plaintext attack that gets the RSA private key used to
>authenticate messages. As far as I am aware (and I may not be aware of
>everything) there is no reference work to support this assumption. If
>the assumption is wrong, then the whole SSL can fall to a selected
>plaintext attack launchable (presumably) through those general purpose
>Java aplets we have heard so much about.
With a mailing list this large and diverse one can reasonably assume a range=
of interests and expertise. What I don't understand is your agnostic stance=
on something as apparently basic as MD5. If computer security is your=
purported area of expertise why have you not reached any firm conclusions=
about it? I understand that rigid conclusions are unsafe (eg they'll never=
prove Fermat's last theorem) but it is not like every question is equally=
open. Do you have a realistic attack on MD5 or is this sophomoric claptrap?=
How do you propose to generate messages with specific message digests?=
Assuming you could somehow, how do you proceed to use that information to=
your advantage? So let's say I have a message digest and I'm retrieving the=
allegedly corresponding message which you have the opportunity to alter to=
your heart's content. How would you proceed, even in principle, to defeat=
MD5? I realize I might be assuming too much when I posit that I have the=
true MD5 for the message but my understanding is that you feel that MD5=
might be vulnerable. I've given you all the known plaintexts. Is there a=
next step?
+----------------------------------------------------------------------
|Steve Bryan Internet: sbryan@gofast.net
|Sexton Software CompuServe: 76545,527
|Minneapolis, MN Fax: (612) 929-1799
|PGP key fingerprint: B4 C6 E2 A6 5F 87 57 7D E1 8C A6 9B A9 BE 96 CB
+----------------------------------------------------------------------
